This invention relates to a chassis for supporting other parts such as electrical equipment, and more particularly, to a chassis that can be made of sheet stock which is secured together by only screws.
Electrical equipment such as repeater units of telephone systems typically include a shelf-like chassis which supports a plurality of printed circuit (PC) cards and/or channel units. In a prior art cast aluminum shelf, the PC cards are supported between top and bottom cast parts which are supported horizontally between vertically oriented cast side parts. Elongated troughs and oversized holes are formed in the edges of the horizontal members and in the sides, respectively, to facilitate attaching these parts together. The troughs are many times longer than the diameter of selftapping screws that are passed through the holes in the sides without contacting the latter and threaded directly into the troughs to attach these parts together. Since there is nothing to guide or maintain alignment of the screws, they tend to take the path of least resistance and end up skewed in the cast troughs. Also, these cast parts are much thicker than sheet stock which means that they are relatively heavy and consume more storage space in a knocked down state than does sheet stock. Another prior art shelf for a similar application and which is made out of sheet metal requires that each of the side-edges of the horizontal top and bottom parts be bent over to form a lip. Holes are drilled through these lips and the sides for attaching these parts together with nuts and bolts. Alternatively, plug-nuts are pressed into the holes of the lips for receiving the bolts. In another prior art shelf, the sheet metal parts are spot-welded together. These prior art sheet metal shelves require welding and other handwork which are expensive. Also, they have multiple bends in them which makes it difficult to store these shelves in a knocked down state.
An object of this invention is the provision of an improved chassis-shelf and fastening technique therefor.